The National Institute of Science was an organization in the United States of America.

In 1984, the chief scientist at Da Vinci Research Base, Wilson Evergreen, believed that the base's research was being funded by this organizatiom, but the money was actually only being funelled through it by the United States Defense Department. (TOS novel: The Rise and Fall of Khan Noonien Singh, Volume 1)

Presumably this is a reference to the United States National Academy of Sciences.